For spice rub, mix kosher salt, cracked pepper, cumin and brown sugar in small
bowl. Pour mixture onto large plate; roll pork roast in mixture to coat,
pressing gently to help it adhere to all surfaces. Set aside.

For charcoal grill, light about 40 briquettes; when white ash starts to appear,
divide into 2 portions; push to opposite sides of kettle. With a gas grill,
prepare for indirect cooking. Place pork in center of cooking grate; cover. Cook
1 hour; insert instant-read thermometer into middle of meat to check internal
temperature. Cook until desired internal temperature is reached, about 150
degrees for medium, about 30 minutes longer. Remove meat to a platter; let
stand, covered loosely with foil, for 10 to 20 minutes.

Meanwhile, brush cut sides of avocado with olive oil; sprinkle with salt and
pepper. Grill cut-sides down directly over coals or heat source until you see
grill marks, about 5 minutes. Remove from grill; fill with apple salsa. Slice
pork; serve with stuffed avocados.